The present disclosure relates to an image reading apparatus for optically reading an image from a document.
In an image reading apparatus that obtains image data by optically reading an image from a document on which the image is formed, the document is placed on transparent contact glass that is provided on an upper surface of the apparatus, in such a manner that a surface of the document from which the image is read from downward. Illumination light is then irradiated from downward on the surface via the transparent contact glass, and the image is read from downward by an imaging element. For the image to be read appropriately, it is necessary to maintain a state where the document is in close contact with the contact glass. For this purpose, a document pressing plate is used to press, from upward, the document placed on the contact glass.
In some of such image reading apparatuses, a document feeding device may be provided to feed a plurality of document sheets one by one so that images can be read from the document sheets. In that case, since the document feeding device is located above the placed document sheet, the document feeding device is configured to serve as the document pressing plate. Here, since each of the plurality of document sheets is considerably thinner than 1 mm, an interval between the document feeding device (the document pressing plate) and the contact glass is narrow.
On the other hand, for example, when one page of a booklet literature is read, the document feeding device cannot be used. The user needs to place the booklet literature on the contact glass so that a reading-target page faces downward, and cause the reading operation to be performed in that state. In this case, since the booklet literature has a certain thickness, the interval between the document pressing plate and the contact glass is as wide as the thickness of the booklet literature, and the thickness may be equal to or larger than 1 cm.
Ordinarily, the document feeding device (the document pressing plate) is attached to the image reading apparatus such that it can pivot in the vertical direction with respect to the main body of the image reading apparatus that has the contact glass on its upper surface. For this case, there are known some structures that allow documents of various thicknesses to be in close contact with the contact glass. FIG. 5a, FIG. 5b, and FIG. 5c show examples of such structures in three typical states. In a conventional image reading apparatus 2, on an upper surface 90A of a main body 90 of the image reading apparatus 2, a contact glass 91 having a surface that is wide in a horizontal plane is provided, and a document pressing plate 92 is provided above the contact glass 91. The document pressing plate 92 is configured to pivot in the vertical direction around a pivot shaft 92A that is provided on the rear side (the right side in the drawing) thereof and elongates along a direction perpendicular to the paper surface. Since the pivot shaft 92A is located above the upper surface 90A, the pivot shaft 92A is provided in a support portion 93. The support portion 93 is attached to the main body 90 so as to protrude upward from the main body 90. The document pressing plate 92 is attached to the main body 90 via the support portion 93. The support portion 93 is configured to move in the up-down direction with respect to the main body 90 (the upper surface 90A).
FIG. 5a shows a state where the document pressing plate 92 has been pivoted upward (opened). In the state shown in FIG. 5a, the user, in front of the apparatus (on the left side in the drawing), can place a document on the exposed contact glass 91 and then close the document pressing plate 92 by pivoting the document pressing plate 92 counterclockwise in the drawing. FIG. 5b shows a state where a thin document P1 (for example, a sheet of paper) has been placed and the document pressing plate 92 has been closed. When the above-described document feeding device is used, this state is realized automatically. With this configuration, the document P1 is uniformly pressed downward by the document pressing plate 92. In this state, an image obtaining portion 95 provided inside the main body 90 irradiates illumination light L from downward on the document P1 via the contact glass 91, captures an image of the document P1 from downward, and obtains image data.
On the other hand, FIG. 5c shows a state where a thick document P2 (for example, a booklet literature) has been placed in a similar manner, and the document pressing plate 92 has been closed. In this case, the support portion 93 is positioned higher than in the case of FIG. 5b, allowing the pivot shaft 92A to be positioned higher than in the case of FIG. 5b. From the state shown in FIG. 5b, the document pressing plate 92 has moved upward in parallel. As a result, in the state shown in FIG. 5c, as in the case of FIG. 5b, the whole surface of the thick document P2 is uniformly pressed downward by the document pressing plate 92. With this configuration, as in the case shown in FIG. 5b, the image obtaining portion 95 can read the image of the document P2 by irradiating the illumination light L on the document P2 from downward. In this case, different from the case where the document feeding device is used, the user, in front of the apparatus, can place the document P2 on the contact glass 91 and cause the apparatus to perform the reading while pressing the document pressing plate 92 from upward. That is, with this configuration, it is possible to make the document pressing plate 92 press the document so that the whole surface of the document is uniformly in contact with the contact glass 91, and the image obtaining portion 95 can read an image appropriately, regardless of the thickness of the document.